Exhaust gas valve devices may be considered for various functions in exhaust systems. For example, the counterpressure in an exhaust pipe can be specifically temporarily increased by means of an exhaust gas valve device. This can be carried out, e.g., for improving or making possible an exhaust gas recovery. Exhaust gas valve devices are often used to open an additional exhaust gas path, which is blocked in case of small quantities of exhaust gas, within the exhaust system for operating states of an internal combustion engine, in which large quantities of exhaust gas accumulate. Here, the terms “large” and “small” are defined in relation to one another. Consequently, for example, an exhaust system can be adapted to different operating states of the internal combustion engine in terms of the counterpressure and damping action. An exhaust gas path can be blocked by means of the exhaust gas valve device in the case of a partial load, for example, in order to achieve an especially efficient muffling. By contrast, said exhaust gas path is opened in the case of a full load in order to reduce the counterpressure of the exhaust system, which increases the performance of the internal combustion engine for drive purposes. In particular, such exhaust gas valve devices can be embodied on or in mufflers to be able to control at least one of two or more exhaust gas paths there. The controllability of the respective cross section, through which flow is possible, of the respective exhaust pipe includes at least one open position, in which the cross section, through which flow is possible, of the exhaust pipe is minimally reduced, and a closed position, in which the cross section, through which flow is possible, of the exhaust pipe is maximally reduced. Depending on the configuration of the exhaust gas valve device and depending on the application, one or more or any desired intermediate positions may also be adjustable. In the closed position, the cross section to be controlled can be closed fully or up to a desired valve bypass. This valve bypass may be desired, e.g., for an emergency running property of the exhaust system in case the exhaust gas valve device fails in the closed position.
While an exhaust gas valve device may, in principle, have any desired drive, the electric exhaust gas valve device relevant here is equipped with an electric drive, which is, for example, an electric motor with or without gear transmission. The electric drive has a driven shaft which can be driven rotating about an axis of rotation. The exhaust gas valve device is, furthermore, equipped with an exhaust gas valve, which has a valve diaphragm and a drive shaft aligned coaxially to the axis of rotation and which can be rotated about the axis of rotation for controlling the cross section to be controlled. The driven shaft and the drive shaft are now advantageously coupled to one another in a suitable manner for transmitting torques, for which a coupling device suitable for this purpose can, in principle, be used.
The thermal load of the electric drive is often problematic in such electric exhaust gas valve devices. During the operation of the exhaust system, the exhaust gas valve, which is exposed directly to the hot exhaust gas stream, can heat up. At the same time, heat is also introduced into the drive shaft here. The heat also reaches the driven shaft via the coupling device and reaches the thermally sensitive electric drive via this driven shaft as well. The heat-related expansion of the drive shaft via the respective coupling device may also lead to a high axial mechanical load of the electric drive.